The Shiny-Walled Box Thingie-Fool joke

An Amish boy and his father were visiting a nearby mall. They were amazed by almost everything they saw, but especially by two shiny silver walls that moved apart and back together again by themselves. 
The lad asked, "What is this, father?" 
The father (having never seen an elevator) responded, "I have no idea what it is." 
While the boy and his father were watching wide-eyed, an old lady in a wheelchair rolled up to the moving walls and pressed a button. The walls opened and the lady rolled between them into a small room. The walls closed and the boy and his father watched as small circles lit up above the walls. 
The walls opened up again and a beautiful twenty-four-year-old woman stepped out. 
The father looked at his son anxiously and said, "Go get your mother."